1. Field of the Invention
The present invention relates to a high resolution magneto-optic read head.
2. Discussion of the Background
The magneto-optic reading of magnetic tapes or disks using the Faraday effect in a ferrimagnetic garnet placed in contact or close to the magnetic medium is known for example from publications by T. NOMURA (NHK Company). Such a reading mode gives good performance with regard to the minimum detectable signal level (when its amplitude is close to the average amplitude of the noise), in particular for recording on narrow tracks. On the other hand, this reading mode has a rather low resolution, limited both by the resolution of the optical system and by the spatial band (natural dimensions of the domains) of the garnet. It is thus difficult to read signals having wavelengths of less than one micrometer, whereas present-day magnetic tapes allow the recording of signals having wavelengths of 0.5 micrometer or less.
T. NOMURA has described a solution associating with the garnet used as a magneto-optic transducer a magnetic structure providing coupling with the magnetic tape. This structure is a pole piece having microscopic dimensions (thickness 0.6 .mu.m, track width 15 .mu.m, height 25 .mu.m) applied and stuck to the garnet.
It would be possible to consider the use of magneto-optic transducers for the reading of high density multi-track magnetic recordings, but the major problem which arises then is cross talk between tracks. T. NOMURA's present device would not allow such a multi-track device to be produced because of the high track-to-track permeance exhibited by the pole piece. It would be necessary to divide up this pole piece which would present very large production problems.